In general, a front vehicle body is a fame structure at a front side of a vehicle and defines an engine room. The front vehicle body includes a front end module at a front side of the engine room. The front end module has a cooling module and a head lamp mounted thereon. A fender apron member, on which a suspension system is mounted, is installed at both left and right sides of the engine room and provides a space where a wheel is installed. A dash panel is installed in a rear side of the engine room and divides a passenger room and the engine room. Front side members are mounted under the engine room in a length direction of the vehicle and extend in a width direction on both left and right sides of the vehicle. A sub-frame has an engine and a transmission installed in the engine room and the suspension system mounted thereon to support them.
The fender apron member includes a fender apron upper member at an upper portion of the vehicle. A hood for opening and shutting the engine room is rotatably mounted on a top side of the fender apron upper member via a hood hinge.
FIG. 1 is a schematic modeling drawing of a conventional vehicle body, in which hCOG denotes the center of mass of a vehicle, Mcabin denotes a vehicle body rotation moment based on hCOG, LFR_SUSP denotes a distance from a front suspension to hCOG, LRR_SUSP denotes a distance from hCOG to a rear suspension, FFR_SUSP denotes an external force applied to the front suspension, FRR_SUSP denotes an external force applied to the rear suspension, Fs/mbr denotes an external force applied to a front side member when the vehicle collides, and Ff/a_upr denotes an external force applied to a fender apron upper member when the vehicle collides.
An impact force is generated when the vehicle collides against an obstacle at the front first acts as the external force Fs/mbr for the front side member because the front side member extends longer than the fender apron upper member in the length direction of the vehicle and also acts as the external force Ff/a_upr for the fender apron upper member when the collision continues.
The impact external force Fs/mbr applied to the front side member generates moment Mcabin=Fs/mbr*hCOG that rotates the vehicle body in a counterclockwise direction around the mass center point hCOG of the vehicle. The external force FFR_SUSP that presses the vehicle body from the top to the bottom acts on the front suspension due to the moment Mcabin. In contrast, the external force FRR_SUSP that raises the vehicle body from the bottom to the top in the height direction of the vehicle acts on the rear suspension.
Furthermore, a so-called dipping phenomenon in which a front portion and a dipping measuring unit D of the vehicle sink to the ground G as indicated by an arrow is generated due to the moment Mcabin, that is, a major cause. Such a dipping phenomenon hinders the optimal behavior of an airbag, for example, when a collision accident is generated in the vehicle, thereby deteriorating collision safety of passengers.
In particular, a rear portion of the fender apron upper member in the length direction of the vehicle does not have a continuous connection structure with a front pillar and a cowl assembly, but has a step to provide the space where a hood hinge mounted thereon and a hood rotate. Impact energy applied to the fender apron upper member when a collision accident occurs at a front side of the vehicle does not effectively transfer and distribute to other portions of the vehicle body due to the step. As a result, a rear connection portion of the fender apron upper member excessively deforms, thereby worsening the dipping phenomenon of the vehicle.
Accordingly, there is a need for an improved vehicle body structure capable of improving collision stability of passengers by reinforcing structural stiffness for mounting a hood hinge and reducing the dipping phenomenon or the amount of dipping when an accident occurs.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.